Refactor & Improvements

- fixed position of checkbox in comment form
- refactored Subscriber::subscribe() method
- removed Form\Subscribe class in favor of Subscription\Comment (I'll create a similar class for Registration)
- added labels in Settings > Basics for Subscribe in comments & registration
- added method in Setting model to check whether signup confirmation is enabled

lib/Subscription/Comment.php

@@ -0,0 +1,91 @@
+<?php
+namespace MailPoet\Subscription;
+use \MailPoet\Models\Setting;
+use \MailPoet\Models\Subscriber;
+
+class Comment {
+  const SPAM = 'spam';
+  const APPROVED = 1;
+  const PENDING_APPROVAL = 0;
+
+  static function extendForm() {
+    $subscribe_settings = Setting::getValue('subscribe');
+    $label = (isset($subscribe_settings['on_comment']['label'])
+      ? $subscribe_settings['on_comment']['label']
+      : __('Yes, add me to your mailing list.')
+    );
+
+    print '<p class="comment-form-mailpoet">
+      <label for="mailpoet_subscribe_on_comment">
+        <input
+          type="checkbox"
+          id="mailpoet_subscribe_on_comment"
+          value="1"
+          name="mailpoet[subscribe_on_comment]"
+        />&nbsp;'.esc_attr($label).'
+      </label>
+    </p>';
+  }
+
+  static function onSubmit($comment_id, $comment_status) {
+    if($comment_status === Comment::SPAM) return;
+
+    if(
+      isset($_POST['mailpoet']['subscribe_on_comment'])
+      &&
+      filter_var(
+        $_POST['mailpoet']['subscribe_on_comment'],
+        FILTER_VALIDATE_BOOLEAN
+      ) === true
+    ) {
+      if($comment_status === Comment::PENDING_APPROVAL) {
+        // add a comment meta to remember to subscribe the user
+        // once the comment gets approved
+        add_comment_meta(
+          $comment_id,
+          'mailpoet',
+          'subscribe_on_comment',
+          true
+        );
+      } else if($comment_status === Comment::APPROVED) {
+        static::subscribeAuthorOfComment($comment_id);
+      }
+    }
+  }
+
+  static function onStatusUpdate($comment_id, $action) {
+    if($action === 'approve') {
+      // check if the comment's author wants to subscribe
+      $do_subscribe = (
+        get_comment_meta(
+          $comment_id,
+          'mailpoet',
+          true
+        ) === 'subscribe_on_comment'
+      );
+
+      if($do_subscribe === true) {
+        static::subscribeAuthorOfComment($comment_id);
+
+        delete_comment_meta($comment_id, 'mailpoet');
+      }
+    }
+  }
+
+  private static function subscribeAuthorOfComment($comment_id) {
+    $subscribe_settings = Setting::getValue('subscribe');
+    $segment_ids = (array)$subscribe_settings['on_comment']['segments'];
+
+    if($subscribe_settings !== null) {
+      $comment = get_comment($comment_id);
+
+      $result = Subscriber::subscribe(
+        array(
+          'email' => $comment->comment_author_email,
+          'first_name' => $comment->comment_author
+        ),
+        $segment_ids
+      );
+    }
+  }
+}